This invention relates generally to swivel hooks, and more particularly a new and improved swivel hook and its method of manufacture.
Lifting and safety hooks have a wide range of applications in a vast array of industries and recreational pursuits. While there are many different types of hooks that have been designed for many different applications, one particular commonly used hook is known as a swivel hook. In general, a swivel hook comprises a primary body having a hook member at one end and a rotatable or pivotal swivel eye, connector or clevis at the opposite end. Use of the hook enables a load that is secured to the hook portion to be rotated independently of the rope, cable, strap or other tethering apparatus attached to the hook by way of the swivel eye. The ability of its hook portion to rotate independently of its connecting eye makes a swivel hook highly desirable where there is need to prevent rotational movement and/or forces from being transferred from the hook body through to the rope, cable or tether to which the hook is attached. Swivel hooks allow for the accommodation of rotational forces that may be applied to the hook body without the necessity of using intervening devises or swivel connectors. Depending upon the application, the hook may also be equipped with a gatekeeper and one or more of a variety of locking mechanisms to prevent accidental opening of the gatekeeper.
Typically the primary components of a hook are formed from parts that are made by way of either a forging or a stamping process. Traditionally, where a high strength product is required the primary components would have been forged. Forging generally results in a high strength product capable of withstanding significant tensile and/or compressive loading. In contrast, hooks formed from components manufactured through stamping processes are generally limited to loads significantly less than those that may be borne by forged hooks. However, stamped hooks have the advantage of often being lighter and less costly to manufacture.
The fact that stamped hooks are generally less costly to manufacture, together with the realization that although not having the strength of a forged product they nevertheless have more than sufficient strength for a wide variety of applications, has made stamped hooks a desirable alternative to more traditional forged products. Unfortunately an inherent limitation within the stamping process that is carried through to the end product resides in the fact that stamping involves stamping or punching a particular shape from a blank sheet of material. Accordingly, the punched or stamped product is planer in nature, of a relatively constant thickness, and has square side walls that are generally perpendicular to the upper and lower surfaces. Forming rounded edges, posts, or other 3-dimensional features typically requires subsequent machining, which can add significantly to the overall manufacturing costs. Furthermore, while stamped products often exhibit relatively good strength characteristics in compression and tension, their planer nature and uniform thickness often presents a significant limitation with respect to their ability to withstand torsional stress. On the other hand forging permits a wide variety of 3-dimensional design features to be incorporated into the hook, including design features that enhance torsional loading characteristics.
The invention therefore provides a hook that addresses a number of the limitations associated with existing hooks through providing a hook body that may be formed from a stamping process and that is capable of receiving a swivel, connector or clevis thereon without the need for subsequent machining.
Accordingly, in one of its aspects the invention provides A swivel hook comprising a hook body having a generally uniform thickness and stamped from a sheet of material, said hook body having a hook member formed at a first end and a longitudinally oriented stem formed at a second opposite end, said stem having a generally rectangular cross-section; and, a swivel connector pivotally securable over said stem and formed from a forged metal, said swivel connector having a generally circular bore of a size exceeding the rectangular cross-section of said stem such that said stem may be received through said bore to secure said swivel connector to said hook body while permitting rotational movement of said swivel connector about said stem.
In a further aspect the invention provides swivel hook comprising a hook body having a generally uniform thickness and formed by way of a stamping operation, said hook body having a hook member formed at a first end and a generally rectangular, longitudinally oriented, stem formed at a second opposite end, a connector securable over said rectangular stem, said connector having a bore therethrough for receiving said rectangular stem and for securing said connector to said hook body, said connector permitting said hook body to be attached to a rope, cable or tether; and, first and second washers, said first washer received over said rectangular stem between said hook body and said connector and said second washer received over said rectangular stem between said connector and the end of said stem with a portion of the end of said stem extending through said second washer, said second washer secured to said stem and retaining said connector and said first washer in place about said stem, said first and second washers assisting in the transference of torsional loading between said hook body and said connector and tending to maintain said hook body and said connector in a co-planer relationship.
In yet a further embodiment the invention provides a method of constructing a swivel hook, the method comprising: forming a hook body by way of a stamping process wherein the hook body is stamped from material having a generally uniform thickness, said hook body formed with a hook member at a first end and a generally rectangular, longitudinally oriented, stem at a second opposite end, said rectangular stem having a base portion connecting said stem to said hook body and an end portion that terminates in an outwardly disposed tip; forming a swivel connector by means of a forging process, said swivel connector having a first end securable over said rectangular stem of said hook body and a second end adapted to secure said swivel connector to a rope, cable, tether or object, said first end of said swivel connector having a generally circular bore therethrough for receiving said rectangular stem of said hook body, said bore dimensioned so as to permit rotational movement of said swivel connector about said rectangular stem when received thereon; placing a first washer having a rectangular shaped right angled bore over said stem; inserting said rectangular stem through said circular bore in said first end of said swivel connector; placing a second washer having a generally rectangular shaped right angled bore over said rectangular stem and into abutment with said swivel connector with the end of said stem extending through said second washer; and, thereafter, peening said tip of said rectangular stem extending through said second washer to secure said second washer in place over said rectangular stem.
Further aspects and advantages of the invention will become apparent from the following description taken together with the accompanying drawings.